The invention relates to a short-circuit protection circuit for a switching output, the circuit having a non-self-protected semiconductor switch, in particular a field-effect transistor, to whose control electrode a control voltage can be supplied via an input.
Electrical switching outputs should expediently be protected against short circuits which can occur at the output of the switch both to earth and to a supply voltage (for example to a motor vehicle supply voltage). In this case, the operating state at which the switching output switches on, becomes low-impedance, is critical and at which, at the same time, an excessively high voltage occurs across the switching output as a result of a short circuit. In the case of this type of fault, circuit parts can very quickly be destroyed. Special protection measures are required for this purpose.
Until now, it has been normal to use self-protected field-effect transistors, in particular power MOSFETs, whose drain-source path is automatically switched to have high impedance if there is a risk of overloading or overheating. It is disadvantageous in this case that such a special power MOSFET is particularly expensive. Furthermore, this type of protection circuit is not able to reproduce the normal operating state of the circuit automatically once the fault has been rectified.